Comparison of Asthma Phenotypic Characteristics to Exhaled Nitric Oxide: Observations from the ACE Trial

Article Outline

• Rationale
• Methods
• Results
• Conclusions
• Copyright

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Rationale 

Exhaled nitric oxide (FeNO), a noninvasive biomarker for airway inflammation often elevated in asthmatics, may be influenced by phenotypic characteristics specific to inner-city residents.

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Methods 

FeNO, asthma history, asthma control measures, atopy measures, and pulmonary function tests were collected on 546 inner-city residents aged 12-20 enrolling in the Asthma Control Evaluation (ACE) Trial; all participants had persistent uncontrolled asthma. Relationships between baseline FeNO and phenotypic characteristics were determined, using Pearson correlation coefficients.

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Results 

Median FeNO was 31.7 ppb (IQR 14.1-65.1); mean FEV₁ was 92.1 ± 16.6% predicted and mean FEV₁/FVC was 77.8 ± 9.4%. Maximum symptom days self-reported over the prior 2 weeks averaged 5.6 ± 4.6 days. The mean ACT^® score over the last month was 18.2 ± 4.2. Median total IgE was 262 kU/L (IQR 100-658). Participants averaged 4.8 ± 3.4 positive skin tests (14 tested), led by sensitivity to roach, cat, mold, and mite. Correlation coefficients for associations with FeNO were: 0.46 for total IgE (p < 0.001); 0.38 for number of positive skin tests (p < 0.001); -0.21 for FEV₁ (p < 0.001); -0.32 for FEV₁/FVC (p < 0.001); 0.01 for maximum symptom days (NS); and -0.05 for ACT (NS). The correlation coefficients for asthma-related health care use in the prior year were also weak and not significant.

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Conclusions 

FeNO was best correlated with measures of atopy, and only modestly with lung function, in this highly allergic cohort. These data support the role of FeNO, a non-invasive measure of airway inflammation, as an important dimension of asthma control.